ITI, Sontec, and GML are all familiar names when it comes to equalizers, especially in the mastering world. At ITI, George Massenburg and Burgess Macneal would set a sonic blueprint for a new type of EQ, and eventually the two would refine their designs into the GML 8200, Sontec MES-430/432 Series, and more.

Over the past few years, a number of beautiful vintage EQs from these brands (GML 8200, Sontec MEP-250C, MEP-250A) have passed through our doors at the Vintage King Tech Shop. Recently, though, something truly special happened. For the first time in our 30-plus years of restoring and caring for vintage gear, we were fortunate enough to work on the iconic Sontec MES-432C/9.

"It's often considered the Holy Grail of mastering EQs," says Vintage King co-founder Mike Nehra. "It's known for making audio passing through it sound better without changing its fundamental nature."

Before we talk about the MES-432C/9, let's dive a little deeper into the backstory of ITI, Sontec, and GML...

The Creation Of The Parametric EQ

The story of how the ITI ME-130 and ME-230 parametric EQs led to the Sontec MES-432C/9 unfolds over a few decades.

In the mid-1960s, Burgess Macneal was working in his studio and pressing plant when he met 16-year-old George Massenburg. Around 1968, following a sale of the studio to ITI (an A/V production company), Burgess and George began designing a mixing console for the brand.

The duo had a clear plan in place with Burgess handling the overall architecture and George focusing on the preamps and other key circuits. While they agreed that the EQs available at the time were serviceable, they also felt there was room for something better.

"A Pultec's not bad, we thought, but it doesn't do this and didn't do that. So we kept at it," says Burgess Macneal in an Audio Technology interview.

The ME-130 became the final EQ design for the ITI desk, and the ME-230 would soon make its debut as the first commercially available parametric EQ. At the AES Show in 1972, George presented his famous paper, "Parametric Equalization," which changed studio life forever.

Above: Racked pair of ITI MEP-130 EQs originally sold by Vintage King in 2010.

Above: ITI ME-230 originally sold by Vintage King in 2020.

The Formation of Sontec & GML

ITI would eventually go under in 1975, and a few years later, the brand's one and only console would end up at the bottom of the Baltimore Harbor after the houseboat studio it resided in sank.

After the company's dissolution, George teamed with Earth, Wind & Fire to purchase the studio, while Burgess bought the pressing plant, and then managed to buy ITI's engineering, drawings, front panels, and chassis for only $75 more.

Burgess would soon revive the pressing plant, rehire ITI staff, and start making mastering equalizers out of his house. In 1982, George would form GML, or George Massenberg Labs, and start producing the GML 8200.

The Holy Grail Equalizer: Sontec MES-432C/9

Few pieces of outboard gear have earned the acclaim of the Sontec MES-430 and 432 Series equalizers. Long trusted by mastering engineers, these EQs have been used at legendary facilities like Masterdisk, Sterling Sound, Abbey Road Studios, and Capitol Records. The MES-432C/9 in particular is widely regarded as the gold standard.

"It has a beautiful, silky, ultra-smooth top end. You can significantly boost the air frequencies without introducing harshness or graininess. Even with aggressive boosts across its range, it maintains its natural imaging and depth," says Mike Nehra. "It doesn't smear the stereo field, which is why it's been in high-end mastering rooms for decades."

The MES-432C/9’s naming convention is pretty straightforward: M = Mastering, E = Equalizer, S = Switches, 4 = 4U height, 3 = 3 bands per channel, 2 = dedicated shelving bands, and 9 = ±9 dB gain (selectable in 0.5 dB increments up to 3 dB, 1 dB increments from 3 to 9 dB). Models labeled 9 differ from ones labeled 6, which feature ±6 dB gain in 0.5 dB increments.

As a stereo EQ, the MES-432C/9 has three bands for the left channel and three bands for the right channel. Each band section features three knobs, including Q, Frequency, and Gain. Going left to right, let's take a look at each band's settings:

ITI Sontec MES-432C/9 Band Settings

LO Band
Q: 5 to 15 dB
Frequency: 11 Hz to 570 Hz
Gain: -9 to 9 dB

MID Band
Q: 5 to 15 dB
Frequency: 125 Hz to 6800 Hz
Gain: -9 to 9 dB

HI Band
Q: 5 to 15 dB
Frequency: 3400 Hz to 25 kHz
Gain: -9 to 9dB

Each channel of the MES-432C/9 has bi-frequency fixed shelves labeled HI and LO. The LO shelf has a switch that allows you to choose between 50 Hz and 100 Hz. Both EQ channels can be turned on and off independently using the switches in the center of the MES-432C/9, but in some Sontecs, this doesn't mean a hard bypass.

Interested in purchasing a vintage Sontec EQ? Want to grab a modern take on this classic? We can help! Contact a Vintage King Audio Consultant via email or by phone at 866.644.0160.